Created attachment 588188[details][diff][review]
Make js_memcpy and use it in a bunch of places.
I think it'd be nice to have a js_memcpy(dst, src, len) that asserts that src does not fall in the range [dst, dst + len) and use it throughout the engine.
This passes locally, pushing to try.

Comment on attachment 588229[details][diff][review]
Make js_memcpy and use it in a bunch of places.
r+ with more PodCopy/PodAssign in TradeGuts and JSScript::NewScriptFromEmitter (if possible) and with verification that the generated asm isn't any worse.